Shielding system



Jan. 9, 1934. E. R. HENTSCHEL SHIELDING SYSTEM 2 Sheets-Sheet 2 Filed July 3, 1930 INVENTOR. I MME3,2&M u1e1% BY MMQM TTORNEY Patented Jan. 9, I934 Hentschel," deceased, assignor 'to Wiredltad io,

Q 1110., Yo rk a corporation of Dela V 7 i' am' a. r r I 1in :lApplicationfluly3;.1930L"SeriaLNoL465fl24 V I My invention relates, broadly to; an firnproved system of shielding and more particularly to a system "for shielding the circuitsof 'a nelect'r'cn One of the objects of my inventioni to provi'deafcoristruction of electrostatic shield for shielding the grid lead in a shield grid typeof electron: v H: l 11 I 1 g .7 Another object of my inventio'n'is to provide a 107 circuit arrangementfor'an amplification system employing a shield grid electron tube wherein means are provided for electrically shielding the grid lead of the several electron tubes an ain'- plification system.

E A further object of my invention is "to prcvide 'a construction of shield grid electron tube having means for electrically shielding the "grid lead throughout 1 the entire length thereof without leaving any portion thereof unshielded 'exteriorly or interiorly of theelectron tube structureJ-- Other and further objects'ofmy" invention re sideinthe'circuit arrangement and electron tube construction set forth more fully in the specifi- A cation' hereinafter following by refere'nceto the 725? accompanying drawings, wherein:

735 showing the engagementbetween thev electro:

static shield andgthe electron tube structure.

,My invention provides means for in creasing the efficiency; in a shield grid amplification circuit.;, Although the shield grid vacuum tube has an extremely low plate grid feedback-capacity w th n e fi=an t ere 0 e ne li e ac i n between the plate and grid in the tube itself, the circuits and connections customarily used are such that, quite large amounts of. energy areied back; into the grid circuit. This is sometimesre duced by placing the tube in a separate shielded m ar ent ut s lb t l an r dv leads enter this compartmentthereis still an interaction between them. Heretofore while precau tion has beentaken to arrange a shieldgrid inf termediate the control grid andplateflthe shield grid has terminated short'; :of thef ifid lead which extends into the electron tube leavingfa portion oil the grid lead ii'ismeme Ncrmany capacity will exist between the unshielded portion" or the grid lead and associated grid support with espect tothe late electrode and other associatedcir; cults. the construction of -my' invention; I

pi mem w r by th nt n ffth l grid lead 'is"el'e'ctrically shielded both externally and internally of the electron tube structure. That is} the 'electrical' shieldis continuous throughout the length oifthe grid conductor; I

so" construct thevessel which encloses theelectrodes of the electron tube that the shield grid is extended'throughout the entire length of the supporting 'member'swhichcarry the control grid and throughout the lengthof thecontrol grid; per se; The tube is so constructe'd'thatan an nularj neck portion 'of reduced cross-section is provided for exteriorly retaining an electrical shield in position coextensive with'the'shieldgrid interiorly f theelectron tube, The external shield extends throughout the lengthof-the grid 7B lead insofar as ectrical coupling may exist with respect-' to thefplate' electrodeor other parts' 'ofthe electron tube circuit. In this way the'co'n trol grid is completely shielded and internal cal pacityjeifects substantially eliminated andfinter' actionbetween the associated circuit substantial- Referririg to the drawingsin detail, reference character 1 designates the evacuatedvessel of the electron tube structure which contains oppositely directed'cylindi'ical extensions designatedat 2; 3 and 4, throughvwhich the connections to the sev em electrodes within thetube pass. A base of socket portion is indicated at 5" having suitable contact prongs shown atf6; The control grid is represented at '7 supported ona frame structure indicated at'8 which extends through the press 9 in the upper portion of the projection 2 'ofthe Vessel 1 'Thefconnection to the control grid is takentothe extremities oftheframe members 8 as'shown, at 10. The grid lead is of strand C911:- ductor of goodconductivityrepresented generally at 1:111 Theextension 2; of the vessel 1 is'pro l id d withanan ularneck 12' of reduced'crosssectionrimmediately adjacent the screngrld 100 electrode which I have designated at 14'. The screen grid electrode 14 is supported on frame members 15 which extend interiorly of the'electron tube around the press 9 and "to the extrem ity of the p f0lecti'on 2. The shield grid 14 does not, terminate adjacent, thecontrol grid' "7 as heretofore the art butcontinues beyond the control grid Tllafouhd the entire length of the support, :01; thepontrolfgrid. 'Ihe turns of -the -Stil'''li" glldld: Cbntfu'rith'fdffir disposed im' 11'0 mediately adjacent to, the inside wall of the annular neck 12 of the extension 2 of the electron tube vessel. The electrostatic shield of my invention is represented at 16 in the form of a tubular member which extends throughout the length of the grid conductor 11. The tubular shield 16 has a downwardly depending portion 18 illustrated more clearly in Fig. 4 which is slotted as shown at 17 adapted to resiliently engage the upper extension 2 of the electron tube.

As illustrated in Fig. 4, the depending portion 18 of the electrostatic shield 16 has an annular neck 19 adapted to engage the annular neck 12 on the upper extension 2 of the electron tube. The contour of the tubular shield is such that the flexible grid lead may be disposed axially thereof and insulatingly supported away from the interior walls of the shield bysuitable means such as insulator 20. It will be seen that there is electrically continuous shielding for the grid elec-' trode 7, the supporting frames 8 and the grid lead 11. That is there is no electrical gap intermediate the end of the control grid '7 and some portion of the tube structure-for the threading of lines of force and the introduction of retroactive effects.

The arrangement of the tube structure of my invention in a power amplifier system has been shown more clearly in Fig. 2. In this circuitan oscillator has been illustrated at 21 arranged within a shielded cabinet structure indicated at 22. The oscillator is shown controlled by a piezo electric crystal element 23 and as having an oscillatory circuit 24 associated therewith; The power amplifier stages are contained within the shielded compartments 25. and 26. An electrically conductive partition member 25a extends between shielded compartment 25 and shielded compartment 22. An electrically conductive partition member 26a extends between the compartment 26 and compartment 25. The circuits for the several power amplifier stages and the high frequency oscillator have been shown diagrammatically for the purpose of illustrating the relationship of the shield to the screen grid electrode of the power amplifier tubes. The power amplifier tube 1 is shown having the tubular shield 16 extending through partition 25a and establishing electrical connection with the shield by means of the contact springs 27. The capacity coupling between the shield 16 and the screen grid 14 has been indicated by the dotted line condenser 28. By observing the arrangement of the electrodes in the tube structure of Fig. 1, it will ple the tuned output circuit 30 of the power amplifier system is not subject to electrostatic or magnetic coupling with respect to the control grid by reason of the complete isolation of the control grid and grid lead by means of the shield A similar arrangement is provided in compartment 26 where electron tube 31 has its control grid and grid lead isolated from other parts of the tube circuit by means of the, shield 16 mechanically connected with one endof the evacuated vessel constituting the tube 31.

In high power installations I prefer to enlarge the diameter of the tubular shield 16 to offer as little capacity with respect to the grid lead as possible. I prefer to omit the insulation 20 and use a stifl conductor in place of flexible leads eliminating dielectric losses. When it is necessary to interchange the electron tubes, the shield for the grid lead may be readily removed by snapping the end thereof away from the annular neck 12 and removing the conductors 11 from the terminals at the end of the tube. When a replacement tube is inserted in place of the tube which is removed the connecting leads 11 are restored to the points of connection on the tube and the shield again snapped into postion thereby completing the electrostatic shielding for the tube system.

The complete isolation of the control grid and its leads from the plate circuit prevents feedback of energy from the plate to the grid and renders the amplification of the oscillator highly stable, thus increasingthe-efficiency of the operation of the amplification system.

While I have described my invention in one of its preferred embodiments I desire that it be understood that modifications may be made and that no limitations upon my invention are intended other than are imposed by the scope of the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States is as follows:

-1. An electron tube comprising an evacuated vessel having a projecting tubular portion, an annular neck of reduced cross-section 106 disposed along said tubular portion, a multplicity of electrodes disposed within said vessel, one of said electrodes constituting a screen grid, and a conductive shield encircling the tubular portion of said evacuated vessel and engaging the annular 110 neck thereof and establishing electrical couplin to said screen grid.

2. An electron tube comprising an evacuated vessel having a tubular extension thereon, amultiplicity of electrodes disposed Within saidvessel, one of said electrodes constituting a control grid having a supporting member extending through the tubular extension of said vessel and another of said electrodes comprising a screen grid 611-: circling said control grid and extending interiorly 0 of the tubular portion of said evacuated vessel, an annular neck of reduced cross-section in the tubular portion of said evacuated vessel, and an electrostatic shield. encircling. the exterior of the tubular portion of said evacuatedvessel and engaging the annular neck thereof in capacitative relation to the shield grid interiorly of said vessel.

3. An electron tube comprising an evacuated vessel having a tubular extension thereon, a multiplicity of electrodes within said vessel including a control grid, a frame structure supporting said control grid and extending into the tubular extension of said evacuated vessel, an independent frame structure surrounding said aforesaid frame structure, a screen grid carried by said independent frame structure, an annular neck of reduced cross-section in said tubular extension and a conductive shield engaging the annular neck in said tubular extension in capacitative relation to the screen grid interiorly of said evacuated vessel.

4. An electron tube device comprising an avacuated vessel, a tubular extension on said vessel, said tubular extension having anannular neck of reduced cross-section therein, a frame 14; structure disposed axially of said evacuated ves sel and projecting through said tubular extension and forming a terminal exteriorly thereof, a control grid carried by said frame structure, an independent frame structure concentrically dis 150 posed about said aforementioned frame structure interiorly of said evacuated vessel and projecting into the tubular extension of said evacuated vessel, a screen grid carried by said independent frame structure, and extending into said tubular extension beyond said control grid and beyond the frame on which said control grid is mounted, 

